Short answer, no.
The springs and shocks are separate on the 300ZX rear trailing arm whereas it's a single strut in the 280ZX. Not only that but the diff mount is completely different. If you want it to 'slot in' you'll have a lot of trouble, if you don't mind a bit of fabrication, then it wouldn't be a hard task. In the end, it's still probably easier and more effective to go with bolt on brake upgrades, LSD and a set of weld on coils.